Artwork depicting Mars during its Noachian Period, roughly 4100-3700 million years ago. The period is characterised by high rates of meteorite impacts, volcanism and possibly abundant surface water - however, the water is thought to have been localized rather than spanning the planet in oceans, as on Earth. There was no Valles Marineris at this time, although it may have begun to form. The massive volcanoes that today dot the Tharsis region were probably complete by the end of this Period. The atmosphere was more substantial than at present. Also depicted is Phobos, although nobody is really sure when Phobos came to be, or how.